Method and apparatus for managing power in a processing system with multiple partitions

ABSTRACT

A processing system may include a first processing unit for a first partition and a second processing unit for a second partition. To support power management, an interrupt handler in the processing system may receive a standby command from an operating system. In response to receiving the standby command, the interrupt handler may cause the first processing unit to transition into a reduced power mode. After the second partition detects a wake event, the second partition may cause the first processing unit to transition out of the reduced power mode. In an example embodiment, the interrupt handler executes within the first partition, and the first processing unit transitions into the reduced power mode by entering an idle loop within the interrupt handler. The first partition may determine from within the idle loop whether the first partition has been released from the low power state. Other embodiments are described and claimed.

FIELD OF THE INVENTION

The present disclosure relates generally to the field of data processing, and more particularly to methods and related apparatus for managing power in a processing system with multiple partitions.

BACKGROUND

In a processing system where two or more processing cores or hyper-threads (HTs) exist, the operating system (OS) normally owns all of those processing units. When the workload of the processing system is low or idle, the OS may shift all of the processing units into a low power or standby mode. For instance, Revision 3.0a of the Advanced Configuration And Power Interface (ACPI) Specification, dated Dec. 30, 2005 (the “ACPI Specification”) describes standard interfaces for OS-directed configuration and power management on laptops, desktops, and servers. The ACPI Specification may be obtained from www.acpi.info/spec.htm.

However, existing processing systems do not support separate power planes for each processing core or HT. For example, when a conventional platform with two processing cores changes the sleep state of the processing system, the platform must set both of the processing cores to the same ACPI sleep state.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become apparent from the appended claims, the following detailed description of one or more example embodiments, and the corresponding figures, in which:

FIG. 1 is a block diagram depicting a suitable data processing environment in which certain aspects of an example embodiment of the present invention may be implemented;

FIG. 2 is a block diagram providing additional details regarding some of the hardware components in the processing system of FIG. 1;

FIGS. 3 and 4 are flowcharts depicting various aspects of a process for managing power in a processing system with multiple partitions, according to an example embodiment of the present invention; and

FIGS. 5 and 6 are flowcharts depicting various aspects of a process for creating partitions in a processing system, according to an example embodiment of the present invention.

DETAILED DESCRIPTION

In a typical computer, firmware provides the machine instructions that control the system when the system is being powered up or has been reset, but before an operating system (OS) is booted. Firmware may also control certain operations after the OS has been loaded, such as operations for handling certain hardware events and/or system interrupts. The firmware may handle pre-boot and post-boot operations through a set of routines referred to collectively as a basic input/output system (BIOS). Typically, the BIOS provides an interface between hardware components of the system and software components such as the OS.

Some years ago, the extensible firmware interface (EFI) model was announced. Version 1.10 of the EFI Specification, dated Dec. 1, 2002, (the “EFI Specification”) may be obtained from www.intel.com/technology/efi/main_specification.htm. The EFI Specification defines a set of standard interfaces and structures to be provided by low-level platform firmware. Those interfaces and structures may be used for tasks such as loading additional firmware, running pre-boot applications, booting the OS, and providing runtime services after an OS has been booted. The Intel® Platform Innovation Framework for EFI is an example of a platform framework that is based on the EFI model.

There are not expected to be any future versions of the EFI specification. However, in 2006, the Unified EFI Forum released Version 2.0 of the Unified EFI (UEFI) Specification, dated Jan. 31, 2006 (the “UEFI Specification”). The UEFI Specification may be obtained from www.uefi.org/index.php?pg=4. The UEFI specification is based on the EFI specification, with corrections and changes managed by the Unified EFI Forum. In the coming years, EFI-based or UEFI-based platform frameworks may supplant frameworks based on the legacy BIOS model as the frameworks of choice for designing, building, and operating data processing systems.

For purposes of this disclosure, the terms “firmware” and “BIOS” refer to software that may execute in a processing system before the processing system has booted to an OS, software that may provide runtime services that allow the OS or other components to interact with the processing system hardware, and similar types of software components. Thus, the terms “firmware” and “BIOS” include, without limitation, software based on the UEFI model and software based on the legacy BIOS model. Traditionally, firmware has typically been stored in non-volatile memory. In more recent years, however, processing systems have been developed that store firmware in other types of storage devices or obtain firmware from remote repositories.

For purposes of this disclosure, depending upon the particular implementation under consideration, the term “processing unit” may denote an individual central processing unit (CPU) within a processing system, a processing core within a CPU, a logical processing unit such as a hyper-thread (HT), or any similar processing resource, or any collection of such resources configured to operate collectively as a unit. In a system where multiple processing units exist, the OS normally owns all of the processing units. However, virtualization software, such as a virtual machine monitor (VMM), may be used to allocate one processing unit to one virtual machine (VM), and another processing unit to another VM.

Also, in some processing systems, it is possible to hide one or more of the processing units from the OS, for instance by modifying the ACPI tables produced by the BIOS. In some systems it is also possible to hide one or more portions of random access memory (RAM) from the OS. Additionally, in some systems, several peripheral and integrated devices can be hidden from the OS, for example by updating device-hide registers or other locations in the system's input/output (I/O) controller hub (ICH). These techniques may be used to hide devices for debugging purposes.

In addition to conventional uses for debugging purposes, techniques such as those described above may be used to create two (or more) execution environments within a single processing system. Such an execution environment may also be called a partition. For instance, a processing system may include a main partition and a sequestered partition. The main partition may include a general purpose OS (e.g., one of the various Windows®-based OSs, a Linux®-based OS, etc.) and one or more user applications (e.g., a web server, a business application, etc.). The sequestered partition may not be visible to the main OS, and the sequestered partition may be used for a wide variety of applications, including, without limitation, I/O offloading, platform manageability, and/or fault prediction.

An example embodiment involves a software-based method for trapping power management commands (e.g., a standby command) from the OS, and allowing one partition of a processing system (e.g., an embedded or sequestered partition) to remain functional, while another partition (e.g., a main partition) and the devices within that partition are shut down. Also, this functionality may be deployed without requiring any modifications to the OS for the main partition.

FIG. 1 is a block diagram depicting a suitable data processing environment 12 in which certain aspects of an example embodiment of the present invention may be implemented. Data processing environment 12 includes a processing system 20 that includes various hardware components 22 and software components 24. The hardware components may include, for example, one or more processors or CPUs 34, communicatively coupled, directly or indirectly, to various other components via one or more system buses 14 or other communication pathways or mediums. As used herein, the term “bus” includes pathways that may be shared by more than two devices, as well as point-to-point pathways.

In the example embodiment, processor 34 includes multiple processing units, such as a first processing core 30 and a second processing core 32. Alternatively, a processing system may include multiple processors, each having at least one processing unit. The processing units may be implemented as processing cores, as HT resources, or as any other suitable technology for executing multiple threads simultaneously or substantially simultaneously. In the example embodiment, processing unit 30 may serve as an application processor (AP) for processing system 20, and processing unit 32 may serve as a bootstrap processor (BSP).

As used herein, the terms “processing system” and “data processing system” are intended to broadly encompass a single machine, or a system of communicatively coupled machines or devices operating together. Example processing systems include, without limitation, distributed computing systems, supercomputers, high-performance computing systems, computing clusters, mainframe computers, mini-computers, client-server systems, personal computers (PCs), workstations, servers, portable computers, laptop computers, tablet computers, personal digital assistants (PDAs), telephones, handheld devices, entertainment devices such as audio and/or video devices, and other devices for processing or transmitting information.

Processing system 20 may be controlled, at least in part, by input from conventional input devices, such as a keyboard, a pointing device such as a mouse, etc. Input devices may communicate with processing system 20 via an I/O port 76, for example. Processing system 20 may also respond to directives or other types of information received from other processing systems or other input sources or signals. Processing system 20 may utilize one or more connections to one or more remote data processing systems 70, for example through a network interface controller (NIC) 74, a modem, or other communication ports or couplings. Processing systems may be interconnected by way of a physical and/or logical network 72, such as a local area network (LAN), a wide area network (WAN), an intranet, the Internet, etc. Communications involving network 72 may utilize various wired and/or wireless short range or long range carriers and protocols, including radio frequency (RF), satellite, microwave, Institute of Electrical and Electronics Engineers (IEEE) 802.11, 802.16, 802.20, Bluetooth, optical, infrared, cable, laser, etc.

Within processing system 20, processor 34 may be communicatively coupled to one or more volatile or non-volatile data storage devices, such as RAM 26, read-only memory (ROM) 28, and one or more mass storage devices 38. The mass storage devices 38 may include, for instance, integrated drive electronics (IDE), small computer system interface (SCSI), and serial advanced technology architecture (SATA) hard drives. The data storage devices may also include other devices or media, such as floppy disks, optical storage, tapes, flash memory, memory sticks, compact flash (CF) cards, digital video disks (DVDs), etc. For purposes of this disclosure, the term “ROM” may be used in general to refer to non-volatile memory devices such as erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash ROM, flash memory, etc.

Processor 34 may also be communicatively coupled to additional components, such as one or more video controllers, SCSI controllers, network controllers, universal serial bus (USB) controllers, I/O ports, input devices such as a camera, etc. Processing system 20 may also include one or more bridges or hubs, such as a memory controller hub (MCH) 16, an ICH 18, a peripheral component interconnect (PCI) root bridge, etc., for communicatively coupling system components. In the example embodiment, MCH 16 and ICH 18 are part of a chipset 17.

Some components, such as NIC 74, for example, may be implemented as adapter cards with interfaces (e.g., a PCI connector) for communicating with a bus. Alternatively, NIC 74 and other devices may be implemented as on-board or embedded controllers, using components such as programmable or non-programmable logic devices or arrays, application-specific integrated circuits (ASICs), embedded processors, smart cards, etc.

In the example embodiment, processing system 20 uses firmware-based partitioning. Specifically, after processing system 20 has been started or powered on, firmware 44 may create a main partition 50 and a sequestered partition 52 within processing system 20. Main partition 50 may include the firmware code (e.g., BIOS 40) and the OS code (e.g., OS 60) running on the BSP. Sequestered partition 52 may include the firmware code (e.g., BIOS 42) and the OS code (e.g., OS 62) running on the AP. The main partition may also be referred to as a non-sequestered partition. The sequestered partition may also be referred to as an embedded partition. In alternative embodiments, partitions may run on other types of processing units.

In the example embodiment, ICH 18 includes configuration constructs such as device hide registers 94 that allow various components or devices within processing system 20 to be disabled or hidden. For instance, the configuration constructs may be used to cause ICH 18 to block configuration cycles for certain devices. Also, in the example embodiment, ACPI parameters 90 for main partition 50 may be used to hide processing unit 32 and one or more portions of RAM 26 from OS 60, while ACPI parameters 92 for sequestered partition 52 may be used to hide processing unit 30 and other portions of RAM 26 from OS 62.

Additional details about device hide registers and related topics may be obtained from the Intel® I/O Controller Hub 6 (ICH6) Family Datasheet, dated January 2004 (the “ICH6 datasheet”). The ICH6 datasheet may be obtained from wvw.intel.com/design/chipsets/datashts/301473.htm. Additional details about ACPI parameters and related topics may be obtained from the ACPI Specification at the Internet location referenced above. An example embodiment of a process for creating multiple partitions in a processing system is described in detail below with regard to FIGS. 5 and 6.

In alternative embodiments, other data storage constructs within an ICH and/or within one or more other components may be used to disable or hide devices within a processing system, and other techniques may be used to hide processing units and portions of RAM.

The invention may be described herein with reference to data such as instructions, functions, procedures, data structures, application programs, configuration settings, etc. When the data is accessed by a machine, the machine may respond by performing tasks, defining abstract data types or low-level hardware contexts, and/or performing other operations, as described in greater detail below. The data may be stored in volatile and/or non-volatile data storage. For purposes of this disclosure, the term “program” covers a broad range of software components and constructs, including applications, drivers, processes, routines, methods, modules, subprograms, handlers, etc. The term “program” can be used to refer to a complete compilation unit (i.e., a set of instructions that can be compiled independently), a collection of compilation units, or a portion of a compilation unit.

Thus, the term “program” may be used to refer to any collection of instructions which, when executed by a processing system, perform a desired operation or operations. For instance, ROM 28, data storage device 38, and/or RAM 26 may include various sets of instructions which, when executed, perform various operations. Such sets of instructions may be referred to in general as software.

In the example embodiment, processing system 20 uses techniques such as those described above to create two distinct partitions in processing system 20: main partition 50 and sequestered partition 52. In alternative embodiments, a processing system may have more than one main partition and/or more than one sequestered partition.

In the example embodiment, the components that constitute main partition 50 and sequestered partition 52 are loaded into, and operate from, RAM 26. For example, SMI handler 80 may be loaded into RAM 26 as part of main partition 50, and SMI handler 82 may be loaded into RAM 26 as part of sequestered partition 52. In alternative embodiments, some portions of one or more partitions may reside in other hardware components, such as within a processing unit or a chipset.

In one example embodiment, each partition receives its own OS and its own applications. The OS 60 for main partition 50 may be the same as, or different from, the OS 62 for sequestered partition 52. Also, the programs or software components 24 in processing system 20 may include a distinct instance of firmware 40 for each partition. For instance, each partition may receive some or all of the firmware code 44 from ROM 28. One instance of firmware 44 may be loaded into each partition, for example. Alternatively, processing system 20 may load slightly different instances of BIOS code into the different partitions. For example, as illustrated in FIG. 1, processing system 20 may load BIOS 40 into main partition 50 and BIOS 42 into sequestered partition 52. As described in greater detail below, one or more of the interrupt handlers in BIOS 40 may differ from those in BIOS 42.

In the example embodiment, processing system 20 supports system management mode (SMM), and firmware 44 includes various system management interrupt (SMI) handlers 80, 82. During the pre-boot process, processing system 20 may load SMI handler 80 into main partition 50 as part of BIOS 40, and processing system 20 may load SMI handler 82 into sequestered partition 52 as part of BIOS 42.

As described at www.rcollins.org/ddj/Jan97/Jan97.html, SMM may be used for power management features and other OS independent functions. For instance, MCH 16 and/or other chipset components in processing system 20 may be configured to recognize certain types of events (e.g., timeouts, keyboard input signals, etc.) and to assert SMIs in response to such events. MCH 16 may assert an SMI by asserting an SMI line on bus 14, for instance. Processing system 20 may then enter SMM at the next instruction boundary and save the current state.

While processing system 20 is in SMM, MCH 16 may redirect all memory cycles to a protected area of RAM 26 reserved specifically for SMM. This memory area may be referred to as system management RAM (SMRAM). When SMM is entered, processing unit 30 and processing unit 32 may switch from protected mode to real mode, and each processing unit may save its entire internal state to SMRAM.

After the state has been saved, SMM code may control the operations of processing system 20. For instance, those operations may be controlled by code in the BIOS, such as SMI handler 80 and SMI handler 82. Thus, after the state has been saved, processing system 20 may begin executing SMI handlers 80 and 82. Once SMI handlers 80 and 82 have finished handling the SMI, each handler may execute a resume (RSM) instruction to exit SMM. In response, processing units 30 and 32 may each restore its state, return to protected mode, and resume execution of the program that was running when the SMI was received.

In the example embodiment, SMI handlers 80 and 82 may be similar to each other, but SMI handler 80 includes instructions for handling aspects of power management to be controlled by main partition 50, while SMI handler 82 includes instructions for handling aspects of power management to be controlled by sequestered partition 52.

FIG. 2 is a block diagram providing additional details regarding some of the hardware components in the processing system of FIG. 1. FIG. 2 highlights the partitioning of the expansion slots and integrated devices in an example system. In particular, FIG. 2 shows dotted fill in the blocks for certain devices, to illustrate that those devices, or portions thereof, will be hidden from OS 60. For instance, in the example embodiment, the following components will be made available to sequestered partition 52, but hidden from OS 60 in main partition 50:

-   -   processing unit 32;     -   NIC 74;     -   USB ports 1 and 2; and     -   PCI slots 1 and 2.         The following components may remain visible to, and available         for use by, OS 60:     -   processing unit 30;     -   mass storage device 38;     -   USB ports 3 and 4;     -   PCI-Express (PCI-E) slots 1 and 2; and     -   PCI slots 3 and 4.         Also, in the example embodiment, most of RAM 26 will remain         visible to OS 60, but a portion 27 will be hidden from OS 60 and         made available to sequestered partition 52.

In the example embodiment, the operations for sequestering devices are performed during the pre-boot portion of the initialization process that takes place when processing system 20 is turned on or reset. In one embodiment, BIOS 40 in main partition 50 has primary control of the initialization operations of processing system 20. However, main partition 50 may pass control to sequestered partition 52 when appropriate, for instance to allow BIOS 42 to initialize or configure memory for sequestered partition 52. Additional details concerning an example process for creating partitions in processing system 20 are provided below, with regard to FIGS. 5 and 6.

FIGS. 3 and 4 are flowcharts depicting various aspects of a process for managing power in a processing system with multiple partitions, according to an example embodiment of the present invention. In FIGS. 3 and 4, certain operation blocks are enclosed within larger blocks, referred to herein as “context blocks.” The context blocks labeled “SP OS” denote groups of operations that are performed under control of OS 62 in sequestered partition 52. Similarly, the context blocks labeled “SP SMM” denote operations that are performed by processing unit 32 in SMM mode, possibly under the control of SMI handler 82. Likewise, the “MP OS” context blocks pertain to operations controlled by OS 60 in main partition 50, and the “MP SMM” context blocks pertain to operations performed by processing unit 30 in SMM mode (possibly under the control of SMI handler 80). In addition, the context blocks on the left and right sides of FIGS. 3 and 4 are arranged vertically to show which operations of main partition 50 are performed at approximately the same time as adjacent operations of sequestered partition 52.

The example process depicted in FIG. 3 begins after processing system 20 has booted, with OS 60 executing in main partition 50, with OS 62 executing in sequestered partition 52, and with processing units 30 and 32 operating in a high power or full power mode. For example, processing units 30 and 32 may be in an ACPI maximum processor performance state (P0), within an actively executing processor power state (C0), within a global working state (G0/S0). Alternatively, processing units 30 and 32 may be in a different processor performance state within G0/S0, or similar power consumption states in non-ACPI-based systems.

As indicated at block 210, sequestered partition 52 may be performing value added functions, such as I/O offloading, fault prediction, telephony services such as voice over Internet protocol (VoIP), operations to facilitate local and/or remote platform management, operations to support digital home functionality (e.g., updating lists of available content), etc. At the same time, main partition 50 may be performing additional operations. For instance, a person may be using applications in main partition 50 such as a web browser, a word processor, etc. Accordingly, OS 60 may be dispatching user mode threads, as indicated at block 310.

It may be desirable to keep some or all of the applications in sequestered partition 52 running, even when none of the applications in main partition 50 is being used. For example, a laptop computer may include, among other applications, a web browser in a main partition and a digital video recorder (DVR) application in a sequestered partition. When no one is using the web browser, it may be beneficial to put the main partition in a low power mode. However, at the same time, it may desirable to keep the sequestered partition at a high power or full power state, for instance to allow the DVR application to record a preselected television program.

At block 312, OS 60 may determine whether it has received a standby request. For instance, a standby request may be sent to OS 60 in response to a user event (e.g., when the user selects a standby option from a power management menu of OS 60) or a power management event (e.g., when a timer expires to indicate that processing system 20 or main partition 50 has been idle for a predetermined period of time). If OS 60 has not received a standby request, processing unit 30 may remain in a high-power state, and OS 60 may continue dispatching user mode threads.

However, if OS 60 has received a message or event indicating that processing system 20 or main partition 50 should enter a low power or standby mode, OS 60 may shut down internal and/or peripheral devices assigned to main partition 50, as indicated at block 314. Those peripherals may include, for example, video adapters, hard disks, USB controllers, network interface controllers (NICs), etc. As shown at block 316, OS 60 may then use an ACPI port to instruct BIOS 40 to put processing unit 30 into a sleep state, such as the S1 sleep state within the G1 global sleep state. For purposes of this disclosure, the terms “standby command” and “power reduction command” refer to any command or request from an OS to a BIOS to enter a reduced power state.

In response to the standby command, BIOS 40 may write values to chipset 17 to indicate that chipset 17 is to put processing unit 30 into a reduced power mode, such as the S1 sleep state, as shown at block 320. For instance, BIOS 40 may write a predetermined value to a sleep type (SLP_TYP) field in an ACPI register in chipset 17. As indicated at line 220, when BIOS 40 updates the SLP_TYP field, chipset 17 may respond by issuing an SMI. For purposes of this disclosure, such an SMI may be referred to as a standby SMI.

A conventional SMI handler in a conventional processing system may respond to a standby SMI by updating the sleep enable (SLP_EN) field in the ACPI register, thereby instructing the chipset to switch to the sleep state indicated in the SLP_TYP field. However, in the example embodiment, standby SMIs trigger SMI handler 80 in main partition 50 and SMI handler 82 in sequestered partition 52, as indicated at blocks 324 and 224, respectively. SMI handlers 80 and 82 do not update the SLP_EN field, but instead keep processing system 20 in the S0 state, so that sequestered partition 52 can continue to run. As indicated below with respect to FIG. 4, when the user wants to awaken main partition 50, the user can press the power button to cause SMI handler 82 to briefly switch the system to S1, so that when OS 60 resumes, chipset 17 indicates that processing system 20 in fact went to sleep.

Referring again to FIG. 3, as indicated at block 330, SMI handler 80 may determine whether the SMI represents a sleep or standby command. If the SMI does not represent a sleep or standby command, SMI handler 80 may process the SMI normally, as shown at block 332. Otherwise, SMI handler 80 may enter an idle loop designed to reduce the amount of power consumed by processing unit 30. SMI handler 80 may thus transition main partition 50 into a reduced power mode.

For instance, the process may pass through page connector B, and SMI handler 80 may execute a pause instruction, as indicated at block 334 of FIG. 4. As indicated at block 340, SMI handler 80 may then determine whether sequestered partition 52 has released main partition 50 from low power mode. This determination may be made by reference to a predetermined flag in a shared memory area, or through use of any other suitable approach to passing data. As described below with regard to block 232, in the example embodiment, SMI handler 82 sets a power mode flag or power mode indicator to keep main partition 50 in low power mode. As indicated by the arrow from block 340 returning to block 334, if sequestered partition 52 has not released main partition 50 from low power mode, SMI handler 80 may remain in the idle loop and continue executing pause instructions. However, if sequestered partition 52 modifies or clears the power mode flag to release main partition 50 from low power mode, SMI handler 80 may terminate the idle loop, transition processing unit 30 from SMM to protected mode, and return control to OS 60. SMI handler 80 may thus cause main partition 50 to leave the reduced power mode.

For purposes of this disclosure, the term “pseudo standby” refers to a state of a partition of a processing system, in which the processing unit or units in that partition are in an active power state (e.g., the ACPI S0 power state), but the processor or processors are consuming less power than when executing typical user mode threads, and the partition will keep the power consumption of the processor or processors low until the partition is instructed to leave the reduced power mode.

As shown at block 342, after main partition 50 exits SMI handler 80, OS 60 may determine whether the power button wake status (PWRBTN_STS) bit in the power management 1 status (PM1_STS) register is set. If that bit is set, OS 60 may restart the video controller or controllers associated with main partition 50, if any.

As shown at block 350, OS 60 may then determine whether the sleep state has been completed, for instance by checking whether the wake status (WAK_STS) bit is set. Once that the WAK_STS but has been set, OS 60 may restart any necessary peripherals or devices for main partition 50, and main partition 50 may then resume high power or full power operation, as shown at block 352. For example, the process may pass through page connector D, and OS 60 may dispatch user threads, etc, as indicated above.

Referring again to block 224 of FIG. 2, after sequestered partition 52 receives the SMI, SMI handler 82 may determine whether the SMI represents a standby command, as shown at block 230. If the SMI is not a standby command, SMI handler 82 may handle the SMI normally, as shown at block 232. Otherwise, SMI handler 82 may set a power mode flag, as shown at block 234. The power mode flag may by used to keep main partition 50 in low power mode, as indicated above with regard to block 340. SMI handler 82 may then transition processing unit 32 from SMM to protected mode, and may return control to OS 62. The process may then pass through page connector A, and sequestered partition 52 may resume execution of its usual functions, as shown at block 236.

Also, as indicated at block 240, OS 62 may monitor the power button of processing system 20, for example by periodically reading the PWRBTN_STS bit in chipset 17. The hardware may set the PWRBTN_STS bit when the power button is pressed, and that bit may remain in this state until the software (e.g., OS 62) clears it. As indicated at block 242, if OS 62 detects that the power button has been pressed, OS 62 instructs chipset 17 to switch to the ACPI S1 sleep state, possibly through use of an ACPI port in BIOS 42. Thus, the data or signal which indicates that the power button has been pressed may be considered to be a wake event or wake request.

When OS 62 instructs chipset 17 to switch to the ACPI S1 sleep state, since OS 62 will not yet have cleared the PWRBTN_STS bit, the chipset will immediately return both processing units to the S0 state. A reason for switching chipset 17 to the S1 state is because the subsequent return to the S0 state makes chipset 17 set the WAK_STS bit, and OS 60 checks that bit after sequestered partition 52 releases main partition 50 from the idle loop.

OS 62 may then modify the power mode flag to release main partition 50 from low power mode, as shown at block 244. The modified power mode flag may be considered a wake command. The process may then pass through page connector C, and sequestered partition 52 may continue performing the functions for which it is equipped. Thus, once sequestered partition 52 has released main partition 50 from low power mode, both OSs may resume execution.

In alternative embodiments, after the sequestered partition instructs the main partition to stay in lower power mode, the sequestered partition may also enter a low power mode. For instance, the sequestered partition may transition its processing unit into a sleep state after making arrangements for the sequestered partition to be subsequently awoken. For example, the sequestered partition may set a timer to issue a wake event at a predetermined time (e.g., to record content in accordance with personal video recorder (PVR) settings) or after a predetermined amount of time has passed. Similarly, the sequestered partition may use wake-on-LAN, wake on receiving a VoIP call, and/or any other suitable type of wake event. Thus, alternative embodiments may use processes that differ substantially from the those described on detail above. For instance, a possible scenario is that once the main partition is in pseudo-standby and the sequestered partition has no pending tasks, the sequestered partition could put the system in real standby. Then upon a wake event, the sequestered partition could resume first and then release the main partition from its SMI handler.

Also, the description above focuses on a processing system in which the sequestered partition runs on the BSP and the main partition runs on the AP. However, those roles could be swapped in alternative embodiments of the present invention, with components such as the SMI handlers designed accordingly.

FIGS. 5 and 6 are flowcharts depicting various aspects of a process for creating partitions in a processing system, according to an example embodiment. In particular, FIG. 5 represents the perspective of main partition 50, while FIG. 6 represents the perspective of sequestered partition 52.

FIG. 5 begins with processing system 20 at or near the beginning of an initialization process. That process may have started in response to processing system 20 being powered on or reset, for instance. At block 410, BIOS 40 in main partition 50 may scan all PCI buses in processing system 20, as well as any other buses, and may build a first device list identifying all of the devices discovered on those buses. For instance, in the example embodiment, processing system 20 may scan one or more PCI buses, PCI-E buses, USB buses, industry standard architecture (ISA) buses, etc. In alternative embodiments, other types of buses may be scanned. The process of scanning buses in a processing system to determine which devices are present may be referred to in general as a bus scan. A bus scan may include operations such as the programming of bridges and device base address registers (BARs).

When building the first device list, main partition 50 may include the location information for some or all of the devices discovered during the first scan. For example, the location information may include the bus number, the device number, the function number, and the device type for each discovered device. The device type or any other suitable flag or data item may be used to keep track of which devices are bridges. For bridges, the local information may also identify the type of bridge and may include other information associated with a bridge, such as subordinate bus information.

As indicated at block 412, after the first device list has been built, main partition 50 may program device hide registers 94 and/or similar configuration constructs to hide certain predetermined devices. This programming may set or clear bits in the configuration constructs, based on a pre-selected device distribution. For instance, ROM 28 may have been pre-programmed by a user (e.g., a manufacturer, an administrator, an end user, etc.) with configuration information that specifies which devices are to be used by sequestered partition 52 and hidden from main partition 50. In alternative embodiments, the main partition may retrieve the configuration information from any other suitable data repository.

The configuration information may identify the devices to be hidden by specifying how device hide registers 94 and similar configuration constructs are to be configured. For instance, processing system 20 may assign the device number 0 to a device in the expansion slot labeled PCI 1 in FIG. 2, and if an administrator has configured processing system 20 to hide that device, the configuration information may include data indicating that bit 0 of a Secondary PCI Device Hiding (SPDH) register should be set to 1. The configuration information in ROM 28 may use similar approaches to identify other types of devices to be hidden, such as SATA controllers, an onboard NIC, devices on other types of buses, etc. For instance, the configuration information may include data indicating that main partition 50 is to use a function disable (FD) register to hide particular devices on PCI-E buses, USB buses, etc.

As indicated at block 414, main partition 50 may then perform a second bus scan, and may build a second device list to identify all of the devices detected during the second scan. Main partition 50 may then reset the configuration constructs to unhide or unblock any hidden devices, as indicated at block 416. Also, as shown at block 420, main partition 50 may compare the first and second device lists and produce a list of devices to be sequestered, to include the devices found in the first scan but not in the second scan. The list produced based on the comparison may be referred to as the list of sequestered devices, and that list may include the same type of location information as the first device list, for each device to be sequestered.

As shown at block 422, main partition 50 may then start sequestered partition 52, and may pass the list of devices to be sequestered to sequestered partition 52. Since no devices will be hidden, in accordance with block 416, sequestered partition 52 will be able to read the configuration space of the devices to be sequestered.

As indicated at block 430, after sending the sequestered device list to sequestered partition 52, main partition 50 may wait until sequestered partition 52 has booted. As shown at block 432, after sequestered partition 52 has booted, main partition 50 may again program configuration constructs such as device hide registers 94 to hide the sequestered devices from main partition 50. Main partition 50 may then boot OS 60, as indicated at block 434. The process of FIG. 5 may then end.

The process of FIG. 6 may start in response to the operations depicted at block 422 of FIG. 5, when main partition 50 starts sequestered partition 52. As indicated at block 510 of FIG. 6, once started, sequestered partition 52 may receive from main partition 50 the list of devices to be sequestered. Sequestered partition 52 may then initialize the devices on the list without performing a bus scan.

For instance, sequestered partition 52 may determine whether all of the devices on the list have been initialized, as shown at block 520. If sequestered partition 52 has not yet initialized all of the devices on the list, sequestered partition 52 may select a next device to be initialized, and may use information in the list such as the bus number, the device number, the function number, and the device type for the selected device to locate that device, as shown at block 522. As indicated at block 524, sequestered partition 52 may then initialize that device. When initializing a device, sequestered partition 52 may extract whatever information it requires from the configuration space of that device, and may perform any other operations necessary to configure the device, such as programming BARs of the device and possibly executing an option ROM of the device. However, in the example embodiment, sequestered partition 52 avoids reprogramming any bridges or device BARs, since, depending on the bus topology, reconfiguring bridges or device BARs could render the bridges or devices inaccessible. Also, in the example embodiment, sequestered partition 52 does not initialize any devices that aren't assigned to it (i.e., that are not included in the list of sequestered devices).

Once all of the devices for sequestered partition 52 have been initialized, sequestered partition 52 may boot OS 62, as indicated at block 530, and sequestered partition 52 may use the sequestered devices. The process of FIG. 6 may then end.

Thus, one partition in a processing system may discover locations of devices to be sequestered, and may pass a list with location information for those devices to a second partition. The second partition may then initialize those devices. Device hide registers and/or related configuration constructs may then be programmed to hide or block those devices for the first partition. In the example embodiment, the device hide registers are so programmed before the OS on the first partition boots. In various embodiments, functions like programming the ICH registers to block configuration access to the sequestered devices may be performed by the either partition. In the example embodiment, the location of each sequestered device is provided to the sequestered partition, and the sequestered partition therefore need not perform a bus scan. The sequestered partition may therefore avoid the ambiguous results that could happen if the sequestered partition were to scan buses containing multiple instances of the same type of device (e.g., USB ports). In addition, even though the main partition may set device hide registers and/or related settings after the sequestered partition has booted, the sequestered partition may continue to use the hidden devices since the ICH may block configuration cycles for the sequestered devices, but it may not block access to the I/O addresses and memory mapped registers of those devices.

Also, as indicated above, a processing system may contain more than one main partition, more than one sequestered partition, or multiple main partitions and sequestered partitions. Such processing systems may use variations of the process described above to implement sequestered devices for one or more sequestered partitions.

In the example embodiment, all of the interrupt handlers described above execute on processing units that have access to RAM, that are capable of running full-featured OSs, etc. In one embodiment, those processing units are connected by a main bus (e.g., a front side bus) with no bus bridges interposed between the processing units, although the main bus may use interconnect switches to support communications between the processing units in some embodiments. The interrupt handlers may, in effect, trap the OS standby command and allow the sequestered partition to remain functional while the main partition is put in a low power mode.

In accordance with the description above, embodiments of the present invention may provide for independent partition standby or pseudo-standby without requiring changes to conventional hardware and without requiring changes to conventional OSs. An OS may use conventional power management semantics, yet the platform may enjoy reduced power consumption, as described above. The different partitions in the platform may also run different OSs. Virtualization or server-style hard partitioning is not required to realize the benefits of the teachings described herein.

In light of the principles and example embodiments described and illustrated herein, it will be recognized that the described embodiments can be modified in arrangement and detail without departing from such principles. For example, SMM and SMIs are described above, but alternative embodiments may use other types of execution modes and interrupts, such as platform management interrupts (PMIs).

Also, although the foregoing discussion has focused on particular embodiments, other configurations are contemplated as well. Even though expressions such as “in one embodiment,” “in another embodiment,” or the like may be used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the invention to particular embodiment configurations. As used herein, these terms may reference the same or different embodiments that are combinable into other embodiments.

Similarly, although example processes have been described with regard to particular operations performed in a particular sequence, numerous modifications could be applied to those processes to derive numerous alternative embodiments of the present invention. For example, alternative embodiments may include processes that use fewer than all of the disclosed operations, processes that use additional operations, processes that use the same operations in a different sequence, and processes in which the individual operations disclosed herein are combined, subdivided, or otherwise altered.

Alternative embodiments of the invention also include machine-accessible media containing instructions for performing the operations of the invention. Such embodiments may also be referred to as program products. Such machine-accessible media may include, without limitation, storage media such as floppy disks, hard disks, CD-ROMs, ROM, and RAM, and other detectable arrangements of particles manufactured or formed by a machine or device. Instructions may also be used in a distributed environment, and may be stored locally and/or remotely for access by single or multi-processor machines.

It should also be understood that the hardware and software components depicted herein represent functional elements that are reasonably self-contained so that each can be designed, constructed, or updated substantially independently of the others. In alternative embodiments, many of the components may be implemented as hardware, software, or combinations of hardware and software for providing functionality such as that described and illustrated herein. The hardware, software, or combinations of hardware and software for performing the operations of the invention may also be referred to as logic or control logic.

In view of the wide variety of useful permutations that may be readily derived from the example embodiments described herein, this detailed description is intended to be illustrative only, and should not be taken as limiting the scope of the invention. What is claimed as the invention, therefore, is all implementations that come within the scope and spirit of the following claims and all equivalents to such implementations. 

1. An apparatus to support power management among multiple processing system partitions, the apparatus comprising: a first interrupt handler to execute in a first partition of a processing system, the first interrupt handler to receive a standby command from an operating system (OS) of the processing system, wherein the processing system includes a first processing unit for the first partition and a second processing unit for a second partition; the first interrupt handler to cause the first processing unit to transition into a reduced power mode in response to the standby command; and a second interrupt handler to detect a wake event at the second partition; the second interrupt handler to cause the first processing unit to transition out of the reduced power mode in response to detecting the wake event, wherein the standby command comprises an interrupt generated by the OS to request a transition to a sleep mode; the first processing unit to transition into the reduced power mode by entering an idle loop within the first interrupt handler; the first partition to determine, from within the idle loop, whether the first partition has been released from the low power state; and the first partition to exit the idle loop and the first interrupt handler, in response to a determination that the first partition has been released from the low power state.
 2. An apparatus according to claim 1, wherein: the OS to issue the standby command executes within the first partition; and the first interrupt handler to transfer control to the OS for the first partition when the first interrupt handler exits the idle loop.
 3. An apparatus according to claim 1, wherein the standby command received by the first interrupt handler comprises an interrupt from the OS requesting a transition to a sleep mode.
 4. An apparatus according to claim 1, comprising: the first interrupt handler to cause the first processing unit to execute one or more pause instructions in conjunction with causing the first processing unit to transition into a reduced power mode.
 5. An apparatus according to claim 1, comprising: the first interrupt handler to cause the first processing unit to transition into a reduced power mode without causing the second processing unit to transition into a reduced power mode.
 6. An apparatus according to claim 1, comprising: the second interrupt handler to set a power mode indicator to indicate that the first partition is to operate in a reduced power mode.
 7. An apparatus comprising: a first interrupt handler to execute in a first partition of a processing system, the first interrupt handler to receive a standby command from an operating system (OS) of the processing system, wherein the processing system includes a first processing unit for the first partition and a second processing unit for a second partition; the first interrupt handler to cause the first processing unit to transition into a reduced power mode in response to the standby command; and a second interrupt handler to detect a wake event at the second partition; the second interrupt handler to cause the first processing unit to transition out of the reduced power mode in response to detecting the wake event; the second interrupt handler to set a power mode indicator to indicate that the first partition is to operate in a reduced power mode after receiving the standby command; and the second interrupt handler to modify the power mode indicator to release the first partition from the reduced power mode after detecting the wake event.
 8. A method for managing power in a processing system, the method comprising: receiving, at an interrupt handler of a processing system, a standby command from an operating system (OS) of the processing system, wherein the processing system includes a first processing unit for a first partition and a second processing unit for a second partition; in response to receiving the standby command, causing the first processing unit to transition into a reduced power mode; detecting a wake event at the second partition; and in response to detecting the wake event at the second partition, causing the first processing unit to transition out of the reduced power mode, wherein the standby command comprises an interrupt generated by the OS to request a transition to a sleep mode; the interrupt handler executes within the first partition; the first processing unit transitions into the reduced power mode by entering an idle loop within the interrupt handler; the first partition determines, from within the idle loop, whether the first partition has been released from the low power state; and in response to determining that the first partition has been released from the low power state, the first partition exits the idle loop and the interrupt handler.
 9. A method according to claim 8, wherein: the OS to issue the standby command executes within the first partition; and the operation of exiting the idle loop and the interrupt handler comprises transferring control from the interrupt handler for the first partition to the OS for the first partition.
 10. A method according to claim 8, wherein the operation of receiving a standby command from an OS comprises: receiving an interrupt requesting a transition to a sleep mode.
 11. A method according to claim 8, wherein the operation of causing the first processing unit to transition into a reduced power mode comprises: causing the first processing unit to transition into a pseudo-standby mode.
 12. A method according to claim 8, wherein the operation of causing the first processing unit to transition into a reduced power mode comprises: executing one or more pause instructions in the first processing unit.
 13. A method according to claim 8, comprising: causing the first processing unit to transition into a reduced power mode without causing the second processing unit to transition into a reduced power mode.
 14. A method according to claim 8, further comprising: after receiving the standby command, setting a power mode indicator to indicate that the first partition is to operate in a reduced power mode.
 15. A method comprising: receiving, at an interrupt handler of a processing system, a standby command from an operating system (OS) of the processing system, wherein the processing system includes a first processing unit for a first partition and a second processing unit for a second partition; in response to receiving the standby command, causing the first processing unit to transition into a reduced power mode; detecting a wake event at the second partition; and in response to detecting the wake event at the second partition, causing the first processing unit to transition out of the reduced power mode; after receiving the standby command, setting a power mode indicator to indicate that the first partition is to operate in a reduced power mode; and after detecting the wake event at the second processing unit, modifying the power mode indicator to release the first partition from the reduced power mode.
 16. A manufacture, comprising: a machine-accessible medium; and instructions in the machine-accessible medium, wherein the instructions, when executed in a processing system that has a first processing unit for a first partition and a second processing unit for a second partition, form one or more interrupt handlers and cause the processing system to perform operations comprising: receiving a standby command from an operating system (OS) of the processing system; in response to receiving the standby command, causing the first processing unit to transition into a reduced power mode; detecting a wake event at the second partition; and in response to detecting the wake event at the second partition, causing the first processing unit to transition out of the reduced power mode, wherein the standby command comprises an interrupt generated by the OS to request a transition to a sleep mode; the standby command is received by an interrupt handler executing within the first partition; the first processing unit transitions into the reduced power mode by entering an idle loop within the interrupt handler; the first partition determines, from within the idle loop, whether the first partition has been released from the low power state; and in response to determining that the first partition has been released from the low power state, the first partition exits the idle loop and the interrupt handler.
 17. A manufacture according to claim 16, wherein: the OS to issue the standby command executes within the first partition; and the operation of exiting the idle loop and the interrupt handler comprises transferring control from the interrupt handler for the first partition to the OS for the first partition.
 18. A manufacture according to claim 16, wherein the operation of receiving a standby command from an OS comprises: receiving an interrupt requesting a transition to a sleep mode.
 19. A manufacture according to claim 16, wherein the operation of causing the first processing unit to transition into a reduced power mode comprises: causing the first processing unit to transition into a pseudo-standby mode.
 20. A manufacture according to claim 16, wherein the operation of causing the first processing unit to transition into a reduced power mode comprises: executing one or more pause instructions in the first processing unit.
 21. A manufacture according to claim 16, wherein the instructions, when the interrupt handler for the first partition causes the first processing unit to transition into a reduced power mode without causing the second processing unit to transition into a reduced power mode.
 22. A manufacture according to claim 16, wherein the instructions, when executed, set a power mode indicator to indicate that the first partition is to operate in a reduced power mode, after receiving the standby command.
 23. A manufacture comprising: a machine-accessible medium; and instructions in the machine-accessible medium, wherein the instructions, when executed in a processing system that has a first processing unit for a first partition and a second processing unit for a second partition, form one or more interrupt handlers and cause the processing system to perform operations comprising: receiving a standby command from an operating system (OS) of the processing system; in response to receiving the standby command, causing the first processing unit to transition into a reduced power mode; detecting a wake event at the second partition; and in response to detecting the wake event at the second partition, causing the first processing unit to transition out of the reduced power mode; setting a power mode indicator to indicate that the first partition is to operate in a reduced power mode, after the standby command is received; and modifying the power mode indicator to release the first partition from the reduced power mode, after the wake event is detected at the second processing unit. 